there are 3 basic bolt sizes that have come to be over the years...
Top to bottom in the pic and the order in which they were introduced to the general public:

---YEAR-----------Length--------------
-Pre2k xxx
-Evo xxx
-2k+ xxx
Length is measured from tip to center of pull pin hole

Notice that the pre2k and Evo length bolts are longer in the back. From center hole to back of back block will be 1/2", while the 2k+ is 1/4".

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